Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $87.47   9.825%   $96.0639   $96.06   $96.05   $96.10  
  Purchase #2 $193.25   10.355%   $213.261   $213.26   $213.25   $213.30  
  Purchase #3 $211.92   4.667%   $221.8103   $221.81   $221.80   $221.80  
  Purchase #4 $194.86   5.292%   $205.172   $205.17   $205.15   $205.20  
  Purchase #5 $117.30   11.274%   $130.5244   $130.52   $130.50   $130.50  
  Purchase #6 $222.76   3.617%   $230.8172   $230.82   $230.80   $230.80  
  Purchase #7 $236.57   10.274%   $260.8752   $260.88   $260.90   $260.90  
  7 purchase totals = $1,264.13       $1,358.5240   $1,358.52   $1,358.45   $1,358.60